Conveyor belts are in common use in mines for the transport of ore and debris to and from crushing and milling machines and the like. A problem with conveyor belts is that dust and fine particles of crushed ore and debris can become caked very firmly indeed to the belt, especially if moisture is present. The caked material is not necessarily worthless dirt, but may contain valuable minerals, including gold dust; it is important to scrape the blade clean, not just for the sake of cleanliness, but in order not to waste valuable material.
Scraping caked material from mine conveyor belts is well-known to be a most demanding task. The designer usually approaches the task on the basis of pressing a scraper blade against the (moving) face of the belt. The scraper blade gradually wears down under the abrasive conditions, and one of the problems of belt-scraping lies in providing a scraper blade of sufficient length that the blade has a long service life between replacements.
Another of the problems associated with belt scrapers arises because the belt is not of a uniform thickness. For example, at the joints between sections of the length of the belt the overall thickness of the belt can be greater, which can cause the scraper to "bump" as the belt-joint passes the scraper.
The scraper blade should be able to retract to accommodate this bump; if it cannot retract, the blade (and the belt) may be damaged. It is preferable that this retraction movement, if the scraper is to accommodate the bump easily, be not accompanied by friction, i.e., that the retraction and recovery movement, or the bounce and rebound, should be hysteresis-free.
It is a first aim of the invention to provide a scraper assembly in which the force applied between the scraper blade and the belt remains at a substantially constant or uniform level, even though the scraper may be bouncing and bumping towards and away from the belt, for example because of variations in the thickness of the belt. Bumping and bouncing can also be caused by debris that sticks to the belt with varying intensities of adherence.
It is a second aim of the invention to provide a means for adjusting the position of the scraper blade, relative to the blade housing, to compensate for the gradual wearing away of the blade. Preferably, it is an aim that the adjustment be automatic.